These are some of the system admin tools I have found over the years. Please note that some may be dead projects or not updated in ages. Use at your own risk.
System and network analysis
1. NTFS Permissions Explorer
Using this MMC snap-in you can quickly visualize the user and group permissions of a local or remote folder or drive in a hierarchical format to help identify problems.
2. Xirrus Wi-Fi Inspector
Wi-Fi Inspector is a powerful Wi-Fi management and troubleshooting tool that allows you to locate and verify Wi-Fi devices, detect rogue Access Points, troubleshoot connections, and search for Wi-Fi networks.
Whois performs a lookup of the registration information of a given IP address or domain name.
ShareEnum allows you to scan and view the security settings of file shares on your network.
PipeList displays a list of named pipes on your system, including the number of active instances and the instance threshold.
TCPView allows you to view detailed TCP and UDP connection information in a user friendly format.
7. The Dude
The Dude from MicroTik can automatically scan all devices within a given subnet and then draw and layout a map of your network.
8. Microsoft Baseline Security Analyzer
The MBSA is a tool that can be used to detect missing security updates and typical security misconfigurations.
WireShark is an interactive network protocol analyser and capture utility. It provides for in-depth inspection of hundreds of protocols and runs on multiple platforms.
Look@LAN allows you to quickly scan your network looking for active nodes. It provides monitoring, reporting, logging and OS detection features.
RogueScanner will scan your network looking for rogue devices and access points, classifying them in a way that allows you to quickly see what’s on your network.
12. Capsa Free Network Analyzer
Using this tool you can monitor, troubleshoot and diagnose issues on your network. It has a Microsoft Office-like user interface.
SuperScan is a fast connection-based TCP port scanner, pinger and hostname resolution tool.
Blast is a lightweight TCP service stress test tool that can help pinpoint weaknesses in your network.
UDPFlood is a lightweight UDP service stress test tool that sends out packets to a specified IP or port.
This tool allows you to quickly and easily track and manage your network IP addresses.
NetStumbler is an application that allows you to detect the presence of a wireless network using 802.11a/b/g. It is useful for detecting rogue access points, finding locations with poor signal, verifying network configurations and determining the cause of wireless interference.
PingPlotter is a lightweight tracert application that generates graphs to help you visualize the route of the packets from source to destination.
19. SolarWinds Free Permissions Analyzer for AD
Using this tool you can quickly visualize the user and group permissions of a folder or shared drive in a hierarchical format. It can track share level permissions, provide a breakdown of share level and file level permissions and help identify why certain users have the permissions they do.
20. Angry IP Scanner
Angry IP Scanner is a fast standalone IP address and port scanner.
21. FreePortMonitor FreePortMonitor is a tool for monitoring servers and applications on your network.
WirelessNetView monitors the activity of wireless networks in the area and displays information related to them, such as SSID, Signal Quality, MAC Address, Channel Frequency, etc.
BluetoothView monitors the activity of Bluetooth devices in the area and displays information related to them, such as Device Name, Bluetooth Address, Device Type, etc.
Vision allows you to view all open TCP and UDP ports and then maps them back to the owning process or application.
Attacker is a TCP/UDP port listener that allows you to define a list of ports that you want it to listen on and it will notify you when a connection is established on that port.
26. Total Network Monitor
Total Network Monitor is a comprehensive network monitoring application that allows you to view the state of your network. It is customizable and has advanced alerting features, letting you know when something is wrong.
27. IIS Logfile Analyser
This tool allows you to analyse your IIS logfiles to determine website statistics such as number of visitors, number of downloads, etc.
ntop uses a web-based interface that allows you to monitor network traffic and statistics.
System testing and troubleshooting
Pinkie is a collection of network troubleshooting utilities that allows pinging multiple hosts, forward and reverse DNS lookup, a ping sweeper, and a subnet calculator.
30. VMWare Player
VMWare Player is a multi-platform virtualization solution that can be used to create and run multiple 32-bit or 64-bit virtual machines. Ideal for testing or development environments.
31. Oracle VirtualBox
VirtualBox is a free, multi-platform general-purpose virtualization solution that can be used to create and run multiple virtual machines. Ideal for testing or development environments.
ADInsight is a real-time monitoring tool used for troubleshooting LDAP (Lightweight Directory Access Protocol) clients.
33. Process Monitor
Process Monitor allows you to monitor activity related to processes, threads, DLLs, the registry and file system in real-time. Useful for troubleshooting application and system-related issues.
34. SpiceWorks Network Troubleshooting
SpiceWorks Network Troubleshooting is an all-in-one tool that allows you to perform routine troubleshooting tasks such as killing processes remotely, access devices remotely, ping, tracert and nslookup, and even compare the status of two devices.
RAMMap allows you to analyse physical memory allocation in your system. You are able to determine how much file data is cached in RAM, how much RAM is used by the kernel and device drivers, etc.
Autoruns allows you to view which programs are configured to run at system boot up or login.
Using LogFusion you can view and monitor log files in real-time.
38. Microsoft Log Parser
Using Microsoft Log Parser you can generate a custom-formatted output file containing the results of multiple log file sources such as XML, CSV, Event Logs, or the Registry.
AppCrashView allows you to view Windows Error Reporting (*.WER) files in a simple user interface and then save the results into TXT/CSV/HTML/XML file format.
RootKitRevealer allows you to detect the presence of rootkits that operate by attempting to hide their files or registry entries.
System and network management
41. Bitcricket IP Subnet Calculator
This tool allows you to calculate subnets and CIDR routes automatically using its intuitive interface and auto-discovery feature.
42. EMCO Remote Installer Starter
The free version of EMCO Remote Installer (Starter edition) allows you to perform a software inventory of applications installed on your network. You can retrieve and track changes as well as save reports.
ManagePC allows you to create an inventory of all your machines in the domain, including hardware, software, devices, patches, group policies, etc.
44. Pandora FMS
Pandora FMS is a network monitoring solution that allows you to monitor multiple platforms, from Linux machines, to Solaris machine, to Windows machines. It provides alerts and reporting for CPU, disk and memory usage, temperature, or even application values.
45. SNARE Audit and EventLog Management
SNARE (System iNtrusion Analysis and Reporting Environment) allows you to install agents onto your server machines to facilitate the centralized collection of logs, including Windows, Solaris, AIX, ISA Server, IIS Server, SMTP, Exchange, Apache, etc.
46. OCS Inventory
OCS Inventory is an automated inventory and deployment application. It allows you to determine what devices or software are installed on your network and deploy software or configuration scripts using a simple web-based interface.
47. Zenoss Core – Enterprise IT Monitoring
Using the Zenoss Core application, you can monitor systems availability, performance, events and configuration across the network.
48. Unipress Free Help Desk
Unipress Free Help Desk is a simple yet powerful Help Desk solution that allows you to create, assign and receive issue tickets. It contains a web portal and knowledgebase for self-help.
49. SysAidIT Free Help Desk
Using this tool, you can easily manage and service requests and create an inventory of installed software and network devices on your network.
50. Cyberx Password Generator Pro
Cyberx Password Generator Pro allows you to create random highly secure passwords.
51. KeePass Password Safe
KeePass is a lightweight, user-friendly password manager. It allows you to store all your passwords in a central location that is encrypted using military grade encryption.
Using TweakUAC you can quickly enable, disable UAC or set it to quiet mode.
53. Microsoft Application Compatibility Toolkit
The Microsoft Application Compatibility Toolkit allows you to evaluate and mitigate application compatibility issues during the pre-deployment phase of a Windows 7, Windows Vista, or new Internet Explorer version installation.
54. ExtraSpy Employee Monitor
ExtraSpy Employee Monitor allows you to monitor employee activities across your network to help detect misuse of company property or unproductive individuals.
55. NetWrix USB Blocker Freeware
Using this tool you can centrally manage access control of removable media on your network.
FileZilla is a cross-platform FTP, FTPS and SFTP client.
57. Wake On Lan 2 .NET
The Wake On Lan 2 .NET tool allows you to manually or automatically power on, restart or shutdown machines or devices over your local network.
Speccy is a system information tool that allows you to quickly see comprehensive details related to your machine.
59. Active Directory Explorer (ADExplorer)
ADExplorer is an advanced Active Directory viewer and editor tool. It allows you to navigate through an Active Directory database and view and edit object properties and attributes.
ADRestore allows you to restore deleted Windows Server 2003 Active Directory server objects.
File and disk management
Disk2vhd allows you to create a Virtual Hard Disk (VHD) of a live machine, which can then be loaded using Microsoft Virtual PC or Microsoft Hyper-V.
Using Defragler you can defrag individual files on an NTFS or FAT32 file system.
PageDefrag allows you to view the defragmentation status of the system Page File and Registry Hives and defragments them. It also allows you to defragment events logs and Windows 2000/XP hibernation files.
PsPad is a powerful text editor that can be used as a substitute for Notepad and is useful for creating scripts, programming, file comparison, etc.
Using MD5Summer, you can quickly generate MD5 hashes for files within a folder, allowing you to ensure or verify file integrity.
66. Universal Viewer
Universal Viewer is a multi-format file viewer that allows you to view different file types from a single interface. Supported file formats include Text, Image, MS Office, Audio, Video, amongst others.
FreeCommander is a comprehensive file manager that aims to be an alternative to Windows Explorer.
Using Recuva you can recover files you accidentally deleted from your machine.
69. Steganos LockNote
Steganos LockNote allows you to securely store confidential notes such as license keys, passwords, phone numbers, etc. It uses AES-256 encryption to store your text in a self-executable container that requires a password to open it.
70. Microsoft SyncToy
SyncToy is an application that can be used as a backup utility to synchronized files and folders between two locations.
7-Zip is a powerful file archiving utility with a high compression ratio that supports a multitude of compression formats, including 7z, GZIP, TAR, ZIP, CAB, MSI, etc.
PeaZip is a cross-platform file and archive manager that supports volume spanning, high levels of compression and encryption and support for a wide range of archiving formats.
Bacula is a suite of applications that allow for the backup, recovery and verification of data across a network.
74. Areca Backup
Areca Backup is a file-based backup application that supports incremental, image and delta backups to a local drive or an FTP server.
75. DirSync Pro
Directory Synchronize Pro is a powerful synchronization utility used to synchronize the contents of a directory to a given location. It provides scheduling, filtering, and logging functionality.
76. Amanda Network Backup
Amanda is a powerful multi-platform backup and archiving application that supports tape, disk, and optical media. Using a single master backup server, you can set Amanda to backup multiple clients across your network.
WebSyncrhonizer allows you to manually or automatically backup, replicate and synchronize files to an FTP server or across your network.
78. KGB Archiver
KGB Archiver is a file archiving tool with a high level of compression that uses AES-256 for its encryption feature.
Iometer is a disk I/O performance analysis tool that allows you to perform stress tests and displays the read and write speed of a specified drive.
Notepad++ is a powerful text editor that can be used as a substitute for Notepad and is useful for creating scripts, programming, file comparison, etc.
Performance and availability monitoring
81. ManageEngine Free HyperV Performance Monitor
HyperV Performance Monitor allows you to monitor CPU, Memory, Disk and Network utilization of your Microsoft Hyper-V virtual servers. It displays the results in a dashboard.
Nagios is a powerful network monitoring tool that allows you to ensure that your critical systems, applications and services are always up and running. It provides features such as alerting, event handling, and reporting.
83. ManageEngine Free Exchange Health Monitor
Exchange Health Monitor allows you to monitor CPU and memory resource utilization, mail queue status, POP/IMAP performance counters, mailbox users, etc of your Microsoft Exchange 2003/2007/2010 servers. It displays the results in a dashboard.
84. Kratos Exchange Monitor
Kratos Exchange Monitor will continuously monitor your Microsoft Exchange Servers and provide a real-time view of its health, including mail queues, CPU and memory utilization, hard drive space, etc.
85. ManageEngine Free Windows Health Monitor
Windows Health Monitor allows you to monitor CPU and memory resource utilization, disk usage and I/O, running applications, etc of your Windows Client and Server machines. It displays the results in a dashboard.
86. ManageEngine Free Ping Tool
Free Ping Tool monitors the availability of servers, routers, switches, mail servers and web servers using the power of ICMP ping. It displays the results in a dashboard.
87. ManageEngine Free SQL Health Monitor Tool
The SQL Health Monitor Tool will monitor the performance and availability of your Microsoft SQL Server 2005 and 2008 servers. It can monitor CPU, memory and disk usage, as well as SQL specific parameters such as page reads/writes and buffer cache. It displays the results in a dashboard.
88. ManageEngine Free VM Configuration Tool
Using the VM Configuration Tool you can configure VMWare ESX virtual servers options like increasing or decreasing RAM and allocating more CPUs. It also monitors the performance of the virtual machines, reporting on CPU, memory, disk and network utilization.
89. Kratos Network Device Monitor
This tool allows you to monitor any SNMP devices on your network, ensuring their availability and performance.
90. IxChariot QCheck
QCheck is a small yet powerful network performance management tool that allows you to quickly check network response times, TCP/UDP throughput, streaming traffic, and troubleshoot wireless network performance problems.
A small, lightweight tool for monitoring local and remote hosts to determine if they are alive or not.
92. Remote Desktop Manager
Remote Desktop Manager is a tool that allows you to centrally manage your remote connections. It support RDP, VNC, TeamViewer, FTP, SSH, Telnet, etc.
TightVNC is a cross-platform lightweight application used for remotely administering clients and server machines.
94. Microsoft RDCMan
RDCMan allows you to manage multiple remote desktop sessions from a single interface.
Terminals is a secure multi-tab remote connection management client. It supports both terminal services and remote desktop client and allows you to better manage multiple connections from a single interface.
PsFile displays a list of files on a system that are opened remotely and allows you to close them.
97. Net Tools 5.0
Net Tools is a comprehensive set of monitoring, network scanning, security and administration tools packed into an intuitive and user friendly UI. It includes 175 utilities including an Advanced Port Scanner, TCP Packet Sniffer, Bandwidth Monitor, Hash MD5 Checker, Fast FTP Client, and Standard Encrypter.
98. ManageEngine Free Windows Tools 2
The ‘Free Windows Tools 2’ kit contains a set of free Windows tools for Network Administrators, including the Remote Task Manager Tool, Wake on LAN, Software Inventory Tool, Remote Command Prompt Tool, GPO Update, Shutdown/Restart Tool, Join/Unjoin Computer Tool, Currently Logged On User, Hard Disk Space Detector Tool, Local Users/Groups List Tool, Network Share Browser Tool, and Laptop Battery Power Monitor Tool.
99. Axence NetTools Pro
NetTools Pro is a set of tools that network administrators can use for monitoring, network scanning, security and administration.
100. Free IP Tools
Free IP Tools is a collection of common tools used to troubleshoot network applications and services in a single interface. It includes tools such as PortScan, TraceRoute, Shares, SNMPAudit, etc.
PsTools is a suite of tools that help you to administer your systems. The tools including in the package allow you to display, execute and kill processes remotely, retrieve system and logon information, and control account passwords and services.